Sealed-in contact device having contacts providing for uniform performance characteristics



March 1, 1960 R. NITSCH 2,927,178 SEALED-IN CONTACT DEVICE HAVINGCONTACTS PROVIDING FOR UNIFORM PERFORMANCE CHARACTERISTICS Filed Dec.29, 1958 2 Sheets-Sheet 1 March 1, 1960 R. NITSCH 2,927,178

SEALED-IN CONTACT DEVICE HAVING CONTACTS PROVIDING FOR UNIFORMPERFORMANCE CHARACTERISTICS Filed Dec. 29, 58

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59 7517 EALEDJN: CQNTAC'P- ANCE HARAQI E STIQS Rudolf'Nitsch; Munich,Germany,- assignor to Si'emens Thisinvention is concernedwithsealed-intor-protective.- tube contacts; of the type which areoperatively-actuated responsive to excitation of anenergizingcoilcausingmag.

netic flux to flow through the corresponding contact springs toaetfect.magnetic attractionflhereof; The object of the invention isto providefor uniformperformance characteristics, particularly uniform holdingvalues.

In connection with such sealedeincontacts, therequire- V mentiscften-times posed thatthey exhibit approximately the same, holding,values. The term holding.- valuei. is intended to mean the energizationor excitation produced by the energizing coil, which just suflices tohold a sealedin contact, for example, a make contact, in closedposition. The requirement with respect to uniform performancecharacteristics and identical holding values does not only apply toindividual sealed-in contacts one with respect to the other but also torelays constructed of sealed-in contacts. It must be considered in thisconnection that, if sealed-in contacts provided for relay structuresexhibit considerable variations in their holding values, such variationswill become operative in the form of corresponding variations among theindividual relays and also with respect to time sequences incident tothe opening of the individual contacts of a relay responsive todisconnection of the energizing coil. The different time spacing betweenthe disconnection of energizing coils and the opening of individualcontacts is in many cases undesirable.

The above indicated problem may be solved by subdividing the tolerancerange, given in accordance with fabrication requirements, into severalcloser sub-ranges and selecting the sealed-in contacts in accordancetherewith. However, this calls for an auxiliary wor 'ng step whichrequires accurate checking methods according to the number ofsub-ranges.

The invention shows a way of obtaining a very narrow tolerance range forthe holding value by particular construction of the sealed-in contactsin the fabrication thereof. This is made possible according to theinvention by constructing in arcuate or ball-shaped manner at least thecontact-making point of one contact spring facing the contact-makingpoint of the other contact spring.

The various objects and features of the invention will appear from thedescription which will be rendered below with reference to theaccompanying drawings showing all parts on a grossly exaggeratedenlarged scale so as to bring out details more clearly. In the drawings,

Figs. 1, 2 and 3 show a known sealed-in make contact comprising fi-atcontact springs in closed position from the side (Fig. 1) and showingthe contact points in crosssectional respectively longitudinal andtransverse views (Figs. 2 and 3);

Figs. 4 and 5 indicate the unavoidable relative angular tiltingdisplacement of the contacts extending essentially in two directions;

Figs. 6 to 11 show a sealed-in make contact comprising flat contactsprings with the contact-making points con- DEVIGEv HAVJNGsnQON. AQTJPRQV DING FOR- Patent 2 c sted: s. r ins r o he inven io p s tiqns herof; nd

igs-r and, .1 s a wQ ws of-atco tac pr i h a on c nduce; pq nt acc g. tothe.

Figs. 1, 2; and 3, the flapcontact springeKl andKZ;

overlap by an; amount a. Between the. contact springs and along theoverlap thereof is disposed; an intermediate layer d which ifs-formedbyazmaterial adapted to provide good contact. Thewidtlrof the, contactsprings is m dica ted by 12.; I amounting to u-b is practically equal tothe operatively eifective pole surface pcrrneated;v by the flux. which.holds the contact springs;inclosed position.

However, the contact-making. points or portions; never lie accurately, ii-absolutely; correct mutually. aligned engagement-such as isassumeddnFigs. 1-, 2"and 3 therealways exists some unavoidable angular tiltingdisplacement which may essentially extend in two directions, thesedirections being indicated in Figs. 4 and 5. The angular tiltingdisplacement causes a crowding of the magnetic flux at the place ofleast spacing between the contact springs K1 and K2, such crowding beingindicated in Figs. 4 and 5 by corresponding crowding of the linesextending between the contact regions of the contact springs anddenoting flux lines. It will be readily apparent that this conditionreduces the operatively effective pole surface as compared with Figs. 1,2, 3 in which the pole surface was assumed to be represented by theproduct This reduction of the operatively effective pole surface isindicated in Figs. 4 and 5 by up and bp, respectively.

This alteration of the operatively effective pole surface causes analteration in the forces of attraction and therewith alteration of theperformance characteristics with respect to the holding values. Sincethe causative tilting displacements are practically unavoidable andabove all subject to considerable variations in the amounts thereof, itfollows that the holding values are from contact to contactcorrespondingly different.

The construction of the contact making points of the contact springsaccording to the invention avoids the variations in the operativelyeflective pole surfaces from contact to contact. Figs. 6 to 11 showcooperating flat contact springs made in accordance with the inven tionin all possible positions thereof. Figs. 6 to 8 show the contact springsfrom the side and Figs. 9 to 11 in transverse sections taken along thecontact points.

Fig. 6 indicates the normal contact position. A length X appears enteredon each side of the central point of contact engagement, the combinedlengths XX delimiting the operatively elfective pole surface or area forthe magnetic flux. As will be readily seen from Figs. 7 to 11, theoperatively efiective pole surface or area will remain constant in anypossible angular tilting displacement of the contact springs. This iseven in case of the illustrated extreme angular'displacements (such aswill never occur in practice) due to the arcuate or ball-like formationof the contact-making point of one of the contact springs. The angulartilting displacement of the contact springs may in practice he kept verysmall and formation of the arcuate surface of the contact-making pointon one spring to correspond exactly to a spherical line is accordinglyunnecessary. This will also be seen from the fact that very slightelevations of the contact-making point will Patented 6 various possible.

n withknown sealed-i l contactswith flatcontact.

The operatively effective contact, surface,

suffice with respect to the contact spring level corresponding in heightto about 20% of the contact spring spacing in open contact position.

The construction of the contact springs according to the inventionproduces further advantages: The operatively efiective pole surface canbe provided in predetermined manner by choice of the radius of curvatureof the contact point provided on one of the flat contact springs, thusmaking it possible to determine the desired performance characteristicwith respect to the holding value. The remaining dimensions of thecontact springs remain unaffected and the energization value retains itsoriginal value. This means that the holding value can always bedetermined as desired without afiecting the energization value.

The contact spring made according to the invention as shown in Figs. 12and 13 respectively in top elevation and from the side is provided withthe arcuate elevation E which is in this case produced by stamping.

Changes may be made within the scope and spirit of the appended claimwhich defines what is believed to be new and desired to have protectedby Letters Patent.

I claim:

In a sealed-in contact device having two cooperatively disposedgenerally flat contact springs arranged with the contact-making ends inoverlapping normally open relationship spaced apart by a gap extendingtherebetween, which springs are operatively actuated responsive tomagnetic flux caused to flow therethrough and across said gap to setupmagnetic attraction forces operative to effect attraction between saidcontact-making ends of said springs to place such ends in closedcontact-making engagement, magnetic holding forces being applied to saidsprings to maintain said closed contact-making engagement, wherein saidsprings, owing to fabrication irregularities, may assume angularlytilted position one with respect to the other, thereby adverselyaffecting the magnetic flux effecting attraction therebetween and alsothe magnetic holding forces applied thereto; a device for nullifying theadverse effects of the tilted positions of said springs, said deviceconsisting in providing one of said contct springs with a contact-makingpoint of arcuate configuration facing the contact-making point of theother contact spring and amounting in height to about 20 percent of thenormal spacing between said contact springs in the open positionthereof, thereby causing magnetic attraction and holding flux to flowuniformly across said contact pointsregardless of angularly tiltedpositions assumed by said springs.

References Cited in the file of this patent UNITED STATES PATENTS1,879,131 Dobke Sept. 27, 1932 1,941,273 Prince Dec. 26, 1933 2,506,414Ellwood May 2, 1950

